MCUIO: remove wire interrupt controller
Makefile: first convert bootloader to bin, then to elf

If the hex is directly converted to elf and then linked, the resulting
image is twice as big as it should be. This has probably something to
do with the fact that flash is word addressable (not byte addressable)
on the atmega.
MCUIO i2c: equalize obuf head and tail in case of NAK while sending data
lib/events.c: increase size of events buffer